1. Field of the Invention
The present invention relates to a mechanism for waterproofing an operation member of an interchangeable lens barrel.
2. Background of the Invention
Generally, a switching operation ring, for example, for switching an auto-focussing mode, which is one of the operation members used in an interchangeable lens barrel, has a plurality of switching positions. In order not to easily come off the respective switching positions, the ring is fixed by an engaging member, which is loosened by pushing a disengagement button when the positions are switched.
FIG. 4 shows a typical example of such an operation member, in which a sectional view of the major portions of a switching operation ring are illustrated. A switching operation ring 53 is set between stopper members 51 and 52 so as not to shift in the direction of the optical axis, and is fit around the peripheral surfaces of the stopper member 51, which is a stopper cylinder so as to rotate around the optical axis. The switching operation ring 53 has a knurled part (indicated by a two-dot chain line in the figure) around its pheripheral surface except along an arc having a certain central angle, where an opening 53a is formed, as shown in the figure, and a switching button 54 is provided through the opening 53a.
The bottom of the switching button 54 is engaged with an end of a rotation stopper blade spring 55 for prohibiting rotation. The other end of the rotation stopper blade spring 55, which is arranged in the longitudinal direction along the inner diameter of the switching operation ring 53, is fixed to the switching operation ring 53 by a screw (not shown). And a protruding portion 55a is formed at the end of the rotation stopper blade spring 55.
In this constitution, in order to rotate the switching operation ring 53, the switching button 54 is pushed, thereby disengaging the protruding portion 55a of the rotation stopper blade spring 55 from a groove 51a formed in the stopper member 51.
In the above-mentioned prior art, a clearance is provided the switching button 54 and the brim of an opening 53a of the switching operation ring 53 so that the switching button can smoothly move. Accordingly, if a waterdrop, such as a raindrop splashes over the clearance, as shown by the arrow A, water enters inward through the clearance and damages machine parts and electrical components.